U.S. Pat. No. 4,421,075 teaches apparatus for maintaining a diesel engine at ready to start temperature, starting the engine responsive to the falling of the block temperature to a predetermined low value, and stopping the engine when the block temperature rises to a predetermined high value. U.S. Pat. Nos. 4,419,866 and 4,878,465, which are assigned to the same assignee as the present application, teach refrigeration systems in which an internal combustion engine drives a refrigerant compressor in a start-stop mode to maintain the temperature of a conditioned space within a predetermined temperature range or null band adjacent to a selected set point temperature. The latter patents also teach automatic starting of the engine when the temperature of the conditioned space is satisfied, i.e., in the null temperature band, such as in response to low engine temperature, low battery voltage, the need to defrost, and the like. Such engine starts will be accompanied by operating the associated refrigeration system in cooling and heating cycles, as required, to hold the temperature of the served space in the null band.